I'm pretty sure all the pump attaching bolts go into the water jacket. If you want something a little better than plain tap water, buy a couple of gallons of "filtered" water at Walmart to mix with the antifreeze. No need to go for the pricey distilled stuff- - - - -you're not filling a steam iron or something else that deliberately evaporates it and leaves residue behind. The "reverse osmosis" filter machines that dispense drinking water should be plenty clean for radiators, and you can bring your own containers if you choose. A 1/8" hole drilled into the thermostat will be plenty to prevent an air lock from forming. Just fill the radiator slowly and wait a few minutes before topping it off. Leaving a couple of inches for expansion in the top tank won't hurt if you don't choose to use a catch can.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!